How well does Blender handle multiple instalations side by side?
multiple blender versions on one system should be fine.
Personally, I don't update Blender builds more than 2 times a week, often less. Of course if some needed feature is broken and has been fixed in a recent build then i'll update asap. There's no right or wrong way here, it's more about how much effort you want to stick into being on the cutting edge.
Let's assume you are downloading from Builder bot
The simplest way to do avoid potential collisions is to take control of where your new blender files go. This means not using the installers, but instead unpacking the builds manually and putting them in separate folders.
You can make short-cuts to different Blenders and put them on your desktop, that way loading different instances of blender is easy. Remove the short-cuts of the Blender versions that you don't think you'll need for a while. Use unique icons to quickly identify the Blender (maybe using 3d glasses for the icon in the viewport branch)
Add-ons
Add-ons are an easy issue to get wrong, both locating them and installing.  But it doesn't have to be hard. Each version of Blender will look in several locations for /scripts/addon.
If you have a core of preferred addons, the way to only worry about those once is to make a custom add-ons folder, and tell Blender to also look there for addons. In:

User Preferences &gt; File &gt; Scripts


In this example I have a folder on that path called scripts, inside scripts i have:
scripts/addons
scripts/addons_contrib

This is where I stick the addons (manually) that I always want to have. And this manually setting of the scripts folder is one reason I don't update every day. It could be scripted of course.. :)